Systems and methods for delivering neural therapy correlated with patient status

ABSTRACT

Therapy systems for treating a patient are disclosed. Representative therapy systems include an implantable pulse generator, a signal delivery device electrically coupled to the pulse generator, and a remote control in electrical communication with the implantable pulse generator. The pulse generator can have a computer-readable medium containing instructions for performing a process that comprises collecting the patient status and stimulation parameter; analyzing the collected patient status and stimulation parameter; and establishing a preference baseline containing a preferred stimulation parameter corresponding to a particular patient status.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 12/703,683, filed Feb. 10, 2010, which claims priority to thefollowing U.S. Provisional Applications, each of which is incorporatedherein by reference: 61/151,464, filed Feb. 10, 2009, and 61/224,032,filed Jul. 8, 2009.

TECHNICAL FIELD

The present disclosure relates generally to systems and methods fordelivering neural therapy correlated with patient status.

BACKGROUND

Neurological stimulation or modulation systems have been developed totreat pain, movement disorders, functional disorders, spasticity andvarious other medical conditions. Implantable neurological stimulationsystems may include an implantable pulse generator and one or more leadsthat deliver electrical pulses to neurological or muscle tissue. In manycases, a physician or caregiver may need to set a variety of stimulationparameters or programs for the patient, which may correspond todifferent postures, activities, or comfort levels that are assumed to besuitable for the patient. Generally, spinal cord stimulators provide thepatient with many different stimulation programs, which are initiallyset up by the physician or caregiver with patient feedback. The initialsetup typically occurs immediately after implant. The patient then usesa patient remote control to change between these programs when thepatient's posture, activity, or comfort level has changed. However, inmany cases, the preset stimulation levels established at implant may notbe suitable for the patient due to slight changes in the lead afterimplant, scar tissue build-up around the lead after implant, or due tochanges in pain patterns over time. These changes may require thepatient to routinely adjust the stimulation settings, which requiresoffice visits by the patient. Accordingly, there is a need for improveddevices and techniques for customizing a patient's stimulationparameters and automatically adjusting stimulation levels for differentpatient needs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a therapy system for providing relieffrom chronic pain to a patient in accordance with embodiments of thepresent disclosure.

FIG. 2 is a functional block diagram illustrating logic components of apulse generator suitable for use in the therapy system of FIG. 1 inaccordance with embodiments of the present disclosure.

FIG. 3 is a block diagram illustrating software modules of the pulsegenerator in FIG. 2 in accordance with embodiments of the presentdisclosure.

FIG. 4 is a database schema illustrating an organization of a treatmentprofile in accordance with embodiments of the present disclosure.

FIG. 5 is a flow diagram illustrating a method for stimulating andblocking neuronal tissues in accordance with embodiments of the presentdisclosure.

FIG. 6 is a flow diagram illustrating a method for establishing patientpreferences during a learning phase in accordance with embodiments ofthe present disclosure.

FIGS. 7A-7C graphically illustrate impedance characteristics that may becorrelated with patient state in accordance with further embodiments ofthe present disclosure.

DETAILED DESCRIPTION

Specific details of several embodiments of this disclosure are describedbelow with reference to implantable spinal cord stimulators forstimulating neural structures, and methods for controllably stimulatinga target neural site of a patient. As used herein, the terms“stimulating” and “stimulation” refer generally to signals applied to apatient to elicit a neural response. Unless otherwise specified, thesignals may have an inhibitory or facilitatory effect on the targetneural population. As used herein, the term “stimulator” appliesgenerally to a device that generates and/or directs stimulation signals.Although selected embodiments are described below with respect tostimulating the dorsal column, dorsal root, dorsal root entry zoneand/or other regions of the spinal column to control pain, theimplantable stimulators may in some instances be used for stimulatingother neurological structures, and/or other tissue (e.g., muscletissue). Several embodiments can have configurations, components orprocedures different than those described in this section, and otherembodiments may eliminate particular components or procedures. A personof ordinary skill in the relevant art, therefore, will understand thatthe invention may have other embodiments with additional elements,and/or may have other embodiments without several of the features shownand described below with reference to FIGS. 1-7C.

Several embodiments of the disclosure are directed to spinal cordstimulation devices (e.g., implantable pulse generators) that have anembedded control algorithm configured to monitor one or morephysiological or physical signals from one or more sensors. The sensorscan be inside or outside of the implantable device e.g. a spinal cordstimulation device. The sensors can include, for example, anaccelerometer, a gyroscope, a blood pressure sensor, an impedancesensor, a thoracic impedance sensor, a heart rate monitor, a respirationrate monitor, a temperature sensor, and/or other suitable sensors. Thecontrol algorithm can have two phases—a learning phase and an automaticoperation phase, as described in more detail below. In general terms,the control algorithm collects sensor data and correlates it withpatient-selected signal delivery data during the learning phase. In theautomatic operation phase, the control algorithm receives sensor dataand directs the signal delivery based on the correlation establishedduring the learning phase.

In a representative implementation, the spinal cord stimulation deviceis implanted into a patient. A physician, a device companyrepresentative, and/or other authorized personnel can program the spinalcord stimulation device by setting up one or more stimulation programsfor the patient and allowing the patient to adjust stimulationparameters including, for example, an amplitude, a pulse width, afrequency, and/or other suitable parameters in the individual programs.Once the programs are established, the patient may have the ability tochange only a subset of parameters in an individual program, e.g., onlysignal amplitude. Also, at the initial setup, the physician or thecompany representative can initialize the individual sensors with“normal” or expected values. The physician or the company representativecan also set a confidence interval for the control algorithm, forexample, from about 80% to about 99%, to indicate the end of thelearning phase. The physician or the company representative can also seta delta change threshold for the individual sensors, e.g., using 5-10%of the signal average, for detecting abnormal operations of the spinalcord stimulation device and/or sensor inputs that are outside anexpected range, as described in more detail below.

During an embodiment of the learning phase, the individual sensors arereset and normalized with initial values, and the spinal cordstimulation device is instructed to start learning by starting thecontrol algorithm. In the learning phase, the spinal cord stimulationdevice (e.g., via the control algorithm) can continuously monitor thepatient for a change of operation. The change of operation can includeone or any combination of the following events: (1) a change in astimulation program, (2) a change in a stimulation parameter, and/or (3)a delta change sensed by any of the sensors. The patient, the physician,or the company representative may cause the stimulation program and/orthe parameters to change.

In response to the detected change of operation, the spinal cordstimulation device and/or the control algorithm can record the programsettings, sensor readings, and/or other operational parametersassociated with the change. For example, the control algorithm canrecord the time of day, the patient's body position, the patient'sactivity level, the currently active stimulation program and associatedstimulation parameters, and/or other values. In certain embodiments, thesensor readings can be obtained from a gyroscope that senses a posturechange, from an accelerometer that measures a change of motion, and/orfrom an active electrode on a lead body that measures impedance. Withthe recorded data, the spinal cord stimulation device and/or the controlalgorithm can build a database to associate the stimulation program andparameter settings with one or more sensor readings.

The database can be populated as the control algorithm learns, byrecording the patient inputs. In the learning phase, the patient is incomplete control of the spinal cord stimulation device. For example, anytime the patient goes to sleep and uses “Program 2” (which has, e.g., asignal frequency of 80 Hz, a pulse width of 150 μsec, and an amplitudeof 2.6 mA), the control algorithm populates the database with the timeof day (e.g., nighttime), Program 2, and the parameter settings (e.g.,frequency, pulse width and amplitude). Over a period of time (e.g.,weeks, months, etc.), the spinal cord stimulation device can collectsufficient data to meet the preset confidence intervals and enter theautomatic operation phase based on certain sensor readings.

During the automatic operation phase or automatic phase, the stimulationdevice uses the information in the populated database to set stimulationparameters, given inputs from one or more sensors. For example, thespinal cord stimulation device can enter the automatic phase for atleast some body positions (e.g., standing, sitting, laying, etc., asdetermined by a gyroscope), the gross time of day (e.g., night (sleepingprogram), morning (active program), evening (watching TV program),etc,), and/or other suitable sensor readings. As a result, when thepatient sits down, for example, the spinal cord stimulation deviceautomatically changes the patient stimulation program and/or stimulationparameters to match the patient's preferred values. This change is basedon information that the patient entered during the learning phase,rather than on the initial settings entered by the physician or companyrepresentative.

The length of time required to meet the confidence intervals may bepatient-dependent. Factors that can influence the required amount oftime may include the patient's level of use of the device, the number oftherapy changes needed, and/or other factors which can vary for eachpatient depending on the patient's pain and activity level. In severalembodiments, once the spinal cord stimulation device has met or exceededthe confidence intervals, the control algorithm enters the automaticphase. Not all conditions must be met before the device can enter theautomatic phase. For example, if the spinal cord stimulation devicereaches the preset confidence interval for the laying down body positionduring evening hours, then the spinal cord stimulation device can enterinto the automatic phase for these conditions only, without affectingother conditions. The device can continue to operate in the learningphase or mode to collect data for other conditions. In the foregoingexamples, identifiers such as “laying down” and “evening” are used forillustrative purposes. In actuality, the system can populate thedatabase with raw and/or modified gyroscope data and clock data, withoutthe need for identifiers.

When the spinal cord stimulation device enters the automatic phase, itcan automatically change the stimulation program and/or stimulationparameters for the patient. In certain embodiments, the spinal cordstimulation device can alert the patient before automatically making anadjustment by displaying a message on a patient remote control, byproducing a discrete vibration, and/or by utilizing other suitablemeans. In several embodiments, this alert feature may be removed overtime or eliminated entirely.

The spinal cord stimulation device can continuously check for a changeof sensor readings, a change in stimulation program, and/or a change instimulation parameters that are outside the preset delta changethresholds. If such a change is detected and is outside expected limits,in certain embodiments, the spinal cord stimulation device can alert thepatient that such a change has occurred. In certain cases, e.g. if thelead impedance is out of range indicating a lead failure or otherwise,the spinal cord stimulation system can notify the physician directlythrough the central database, by sending an automatic note (e.g. email,fax, voicemail or otherwise as appropriate) of the patient statuschange. For example, such a change can include a sensor value or apatient-input amplitude that is outside predefined limits, or arequested program change that was not encountered during the learningphase. In response, the patient can override this alert, and the controlalgorithm can record the event as a new database entry and start tolearn more about this new setting, position, stimulation, etc. In otherembodiments, the patient can turn off the stimulation therapy and see aphysician. The physician can then troubleshoot and plan the nexttreatment for the patient. The spinal cord stimulation device canreenter the learning mode to learn the new programs, settings, etc. andswitch to the automatic phase as described above.

FIG. 1 schematically illustrates a therapy system 100 for providingrelief from chronic pain in accordance with embodiments of the presentdisclosure. The therapy system 100 is shown in FIG. 1 positionedrelative to the general anatomy of a spinal cord (labeled “SC” inFIG. 1) of a patient. As shown in FIG. 1, the therapy system 100 caninclude a pulse generator 101. The pulse generator 101 can be implanted,e.g., subcutaneously, within an abdominal or lower back region of thepatient. The pulse generator 101 can be electrically connected to asignal delivery device 112. The signal delivery device 112 can include alead 102 electrically connected between the pulse generator 101 and anelectrode array 103 implanted in close proximity to the spinal cord SC.The signal delivery device 112 can include one or more electrodes orelectrode contacts carried by a support substrate. A representativeelectrode array 103 is disclosed in U.S. patent application Ser. No.12/104,230, filed Apr. 6, 2008, the disclosure of which is incorporatedherein in its entirety by reference. In other embodiments, the signaldelivery device 112 can have other configurations. For example, thesignal delivery device 112 can include one or more electrodes (e.g.,eight electrodes or sixteen electrodes) spaced apart axially andpositioned in one or two rows along the lead 102, in place of theelectrode array 103.

The pulse generator 101 is configured to generate and transmitstimulation signals to the signal delivery device 112. In certainembodiments, the pulse generator 101 can include a logic processorinterconnected with a computer-readable medium containing computerexecutable instructions, and further connected with input/output devices(e.g., wired or wireless transceivers), power management circuitry,and/or other suitable electrical components (not shown in FIG. 1), asdescribed in more detail below with reference to FIG. 2. Thecomputer-readable medium can include volatile and/or nonvolatile media,e.g., read-only memory (ROM), random access memory (RAM), magnetic diskstorage media, optical storage media, flash memory devices, and/orothers. In other embodiments, the pulse generator 101 can also includespecific hardware components having hard-wired logic (e.g.,field-programmable gate arrays) for performing the operations, methods,or processes or with any combination of programmed data processingcomponents and specific hardware components.

In a particular embodiment, the pulse generator 101 includes an embeddedsensing element 126 in electrical communication with the logic processorof the pulse generator 101. The sensing element 126 can include at leastone of a gyroscope, an accelerometer, a laser sensor, a pressure sensor,a temperature sensor, an impedance sensor, a heart rate monitor, arespiration rate monitor, a clock, and/or other suitable sensors formeasuring the current status and/or physiological indicators of thepatient. Even though the sensing element 126 is shown in FIG. 1 asintegrated into the pulse generator 101, in other embodiments, thesensing element 126 can be positioned remotely from the pulse generator101 and coupled to the pulse generator 101 with a suitable link (e.g., awired or wireless link). The system 100 can include a single sensingelement 126, or multiple sensing elements 126 depending on factorsincluding patient condition, patient diagnosis, patient preferenceand/or practitioner preference.

The therapy system 100 can also include a remote control 105 configuredto communicate with and/or control the implantable pulse generator 101.As shown in FIG. 1, the remote control 105 includes a housing 104carrying multiple input devices 106 (e.g., push buttons, track wheels,directional keys, etc.), a display 107 (e.g., a liquid crystal display),and an antenna 108 (e.g., an induction wand). The remote control 105 canalso include internal circuitry (not shown) configured to produce amodulated signal and then transmit (via long range telemetry) themodulated signal to the pulse generator 101. In response to thetransmitted signal, the pulse generator 101 can, for example, modulatethe received signal into a return signal and transmit the modulatedreturn signal carrying requested information to the remote control 105according to a suitable protocol (e.g., frequency shift key, phase shiftkey, quad phase shift key, etc), or adjust its operation by changing astimulation program and/or stimulation parameters. In certainembodiments, the remote control 105 is configured as a handheld device.In other embodiments, components of the remote control 105 can haveother portable or stationary configurations.

Optionally, in certain embodiments, the therapy system 100 can include apersonal computer 110 coupled to the remote control 105 via acommunication link 111 (e.g., a USB link, an Ethernet link, a Bluetoothlink, etc.). In other embodiments, the personal computer 110 can becoupled to a network server 114 via a network connection 113 (e.g., aninternet connection, an intranet connection, etc.) In yet otherembodiments, the personal computer 110 and/or the network server 114 maybe omitted. In further embodiments, the therapy system 100 can alsoinclude routers, switches, data storage centers, and/or other suitablenetwork components.

After implanting the pulse generator 101, a caregiver (e.g., a physicianor a pulse generator company representative) can first configure thepulse generator 101 with an initial set of operating programs and/orparameters using an external programmer (not shown). The caregiver mayfirst configure the pulse generator 101 with an initial set of operatingparameters for different patient status variables, such as for differentpain areas or types and different patient body positions, patientphysical activity levels, time of day, various physiological indicatorsof the patient, and/or other suitable patient status variables. Theinitial set of operating parameters can include frequencies, amplitudes,electrode selections for the signal delivery device 112, and/or othersuitable parameters. For example, in one embodiment, the initial set ofoperating parameters can include a first amplitude for a first bodyposition (e.g., standing) and a second amplitude for a second bodyposition (e.g., lying down). In another embodiment, the initial set ofoperating parameters can also include a first electrode configurationthat relates to a first pain area (e.g. the lower back) and a secondelectrode configuration that relates to a second pain area (e.g. theleft leg). In other embodiments, the initial set of operating parameterscan also include other operating parameters based on the time of day,physiological indicators of the patient, and/or other suitable processvariables. According to the initial set of operating parametersprogrammed, the pulse generator 101 can apply therapy signals (e.g.,electrical impulses) to the nerve fibers of the patient, such as toup-regulate (e.g., stimulate or facilitate) and/or down-regulate (e.g.,block or inhibit) the neural response.

One operational difficulty associated with conventional implementationsof the foregoing technique is that the initial set of parameters may notbe suitable for the patient outside of a clinical setting. For example,without being bound by theory, it is believed that the signal deliverydevice 112 may shift when the patient is active (e.g., when the patientruns, walks, and/or engages in other activities) or when the patientchanges from one body position to another (e.g., among positions such asstanding, sitting, lying down, and/or others). The shifting of thesignal delivery device 112 may render the applied therapy signals lesseffective for relieving pain, and/or may cause patient discomfort. It isalso believed that the patient's perception of pain may be different atdifferent activity levels. As a result, the initial set of parametersfor the pulse generator 101 may not be effective to achieve and/ormaintain treatment efficacy over an extended period of time and/or overthe course of the patient's typical activities. The patient does havethe option of adjusting the stimulation program and/or parameters withthe remote control 105 (e.g., configured as a handheld device), withinthe preset values done at implant. However, the adjustment process usingthe remote control 105 may be cumbersome, restrictive, and/ortime-consuming.

To overcome the above described operational difficulties, the presentlydisclosed therapy system 100 can be configured to (1) establish patientselections (e.g., preferences) during an initial period (e.g., alearning period); and (2) subsequently automatically adjust thestimulation parameters based, at least in part, on (a) the patientpreferences learned during the initial period and (b) the current status(received through the sensors) of the patient. The patient preferencesmay include patient-selected or patient-preferred values of suitablestimulation parameters and may be referred to collectively as apreference baseline. Once the patient preferences are established, thepulse generator 101 can automatically adjust the stimulation parametersprovided to the electrode array 103 in response to a change in thepatient's activity level, body position and/or other variable to improveand/or maintain treatment efficacy, without further input from thepatient.

During the initial (learning) period, the pulse generator 101 cancontinuously monitor the current status of the patient (via the sensingelement 126) and/or the operation of the pulse generator 101 for achange. For example, in certain embodiments, the pulse generator 101 cansense a change when the patient changes at least one of a stimulationprogram (e.g., from a “day” program to a “night” program”), astimulation parameter (e.g., an amplitude and/or a frequency ofstimulation), and/or other suitable parameters. In certain embodiments,the patient can request or implement an increase or decrease in theamplitude of the applied therapy signals using the remote control 105,and the pulse generator 101 records the patient's change and/or anyadjustments to the amplitude. In other embodiments, the pulse generator101 can sense a change of operation under other suitable conditions.

When the pulse generator 101 senses a change of operation, the pulsegenerator 101 can record the values provided by other sensors. Forexample, the pulse generator 101 can record an indication of the currentbody position and/or orientation of the patient with a gyroscopic sensorto determine whether the patient is standing or lying down. The pulsegenerator 101 can sense the patient's current activity level with anaccelerometer to determine a change in the movement of the patientand/or can sense the patient's blood pressure, thoracic impedance,and/or other suitable physiological indicators.

Based on the foregoing recorded measurements, the pulse generator 101can establish the patient preferences. The pulse generator 101 cancorrelate at least one of the patient's indicated changes, the output ofthe pulse generator 101, with at least one of the current body position,the current activity level, and/or other physiological indicators of thepatient. For example, in a particular embodiment, the pulse generator101 can correlate the amplitude of the applied therapy signals with apatient's body position in two dimensions to generate a first preferredamplitude for the stimulation parameters when the patient is standingand a second preferred amplitude when the patient is lying down. Incertain embodiments, each of the preferred amplitudes can be anarithmetic mean of multiple measurements corresponding to each bodyposition, respectively. In other embodiments, the preferred amplitudescan be a median value, a geometric median value, a harmonic mean, aquadratic mean, a weighted mean (e.g., based on time of a day), and/orother values derived from the measurements.

In further embodiments, the pulse generator 101 can correlate severalparameters of the applied stimulation parameters with the patient statusin three, four, five, and/or other numbers of sensor inputs, which maycorrespond to patient activity levels, physiological parameters, and/orother suitable parameters. For example, the pulse generator 101 cancorrelate the stimulation parameters with certain values of both thebody position and the activity level of the patient. As a result, thepulse generator 101 may calculate the preferred amplitude values asshown in the following table:

Position Activity level First selected (e.g., preferred) Standing Mobileamplitude Second selected (e.g., preferred) Standing Immobile amplitudeThird selected (e.g., preferred) Lying down Immobile amplitudeEven though particular values of the patient's position and activitylevel are used in the above example, in other examples, the pulsegenerator 101 can use other values of the patient's position (e.g.,sitting) and/or activity level (e.g., walking, running, etc.). In yetfurther embodiments, the pulse generator 101 can use other patientparameters (e.g. thoracic impedance, heart rate, etc).

In certain embodiments, the initial (learning) period can be apredetermined time period (e.g., 2-5 weeks) set by the caregiver. Inother embodiments, the initial period can be determined by themeasurements recorded and stored in the pulse generator 101. Forexample, the initial period can expire when the derived first and secondpreferred amplitudes have reached a confidence level of at least 80% oranother suitable value. In further embodiments, the patient and/or thecaregiver can terminate the initial period irrespective of an elapsedtime or the current confidence level of the first and second preferredamplitudes and reset the pulse generator 101 with most recent parametersand/or other suitable parameters.

Once the patient preferences are established (e.g., once the learningphase is complete), the pulse generator 101 can automatically adjust thestimulation parameters based on the sensed measurements. For example,when the pulse generator 101 receives an indication that the patient iscurrently standing, the pulse generator 101 can automatically adjust thestimulation parameters (e.g., an amplitude) based on a correspondingvalue of the preferred amplitude in the database for the standingposition. The patient does not have to manually operate the remotecontrol 105 in order to adjust the applied stimulation parameters. As aresult, several embodiments of the therapy system 100 are lesscumbersome, time-consuming, and/or restrictive to operate than areconventional techniques.

After the initial period expires, the pulse generator 101 can continuerecording adjustment inputs from the patient regarding the operatingparameters of the pulse generator 101, the current values of thegenerated stimulation parameters, and/or the current status of thepatient as described above. The pulse generator 101 can periodically(e.g., weekly, biweekly, etc.) or continuously update (e.g., refine) thepatient preferences based on these newly recorded measurements. In otherembodiments, the process of further updating the preferences can beomitted.

In yet further embodiments, if the pulse generator 101 detects a largechange in the patient's status, the pulse generator 101 can output analarm to the patient and/or the caregiver indicating that an additionalassessment is needed. In other examples, the patient and/or thecaregiver can decide when to reestablish patient preferences.

Several embodiments of the therapy system 100 can improve treatmentefficiency for the patient. Instead of estimating the applied therapysignals for each patient status, several embodiments of the therapysystem 100 allow customization of the applied therapy signals based onprevious measurements of the applied therapy signals, thus improving theefficacy of the treatment and/or reducing or eliminating the need forthe patient to manually adjust stimulation settings. In certainembodiments, the therapy system 100 can also provide multiplestimulation levels to individually correspond to different patientstatuses measured by the sensing element 126. For example, if thesensing element 126 indicates that the patient's motion exceeds a firstthreshold, a first stimulation level may be used. If the patient'smotion exceeds a second threshold greater than the first threshold, asecond stimulation level may be used. The caregiver and/or the patientmay select any desired number of stimulation levels and/or thresholds ofpatient status.

Even though the therapy system 100 is described above as establishingthe patient preferences via the implanted pulse generator 101, in otherembodiments, this function can be performed with additional support fromother devices. For example, the pulse generator 101 can transfer therecorded measurements to the optional personal computer 110 and/or thenetwork server 114, and the personal computer 110 and/or the networkserver 114 can establish the patient preferences. In yet furtherembodiments, the patient may establish additional programs for the pulsegenerator 101, and the caregiver may have override capability over theseadditional programs.

FIG. 2 is a functional block diagram illustrating components of thepulse generator 101 of FIG. 1 in accordance with embodiments of thedisclosure. As shown in FIG. 2, the pulse generator 101 can include aradio 118 coupled to an antenna 108, and a processor 120 coupled to aninput/output component 124 and a memory 122. In other embodiments, thepulse generator 101 can also include a battery, a power managementcircuit, or other suitable electronic and/or mechanical components.

The radio 118 can include a frequency modulator, an amplitude modulator,and/or other suitable circuitry for modulating inductive protocols. Theprocessor 120 is configured to provide control signals to and receivedata from the radio 118. In certain embodiments, the processor 120 caninclude a microprocessor, a field-programmable gate array, and/or othersuitable logic components. In other embodiments, the processor 120 mayalso include a detector or a decoder with associated software and/orfirmware to perform detection/decoding functions and process receivedsignals. The memory 122 can include volatile and/or nonvolatile media(e.g., ROM, RAM, magnetic disk storage media, optical storage media,flash memory devices, and/or other suitable storage media). The memory122 can be configured to store data received from, as well asinstructions for, the processor 120. The input/output component 124 caninclude logic components (e.g., a MODEM driver) that receive andinterpret input from the remote control 105 (FIG. 1) as well as hardwarecomponents (e.g., a vibrator) that output information to the patient.

FIG. 3 is a block diagram showing software modules of the pulsegenerator 101 of FIG. 2. Each module is a computer program written assource code in a conventional programming language (e.g., the C++ orJava programming languages) and is presented for execution by a CPU ofthe pulse generator 101 as object or byte codes. The variousimplementations of the source code and object and byte codes can be heldon a computer-readable storage medium such as the memory 122.

As shown FIG. 3, the pulse generator 101 can include three basicsoftware modules, which functionally define the primary operationsperformed by the pulse generator 101: a database module 151, an analysismodule 153, and a processing module 156. In the described embodiment,the processor 120 executes all of these modules in the pulse generator101. However, in other embodiments, these modules can also be executedin a distributed computing environment. The module functions are furtherdescribed below beginning with reference to FIGS. 5 and 6.

As described above, the patient preferences are established during theinitial or learning period. The pulse generator 101 receives aninitially collected sensor data set 157 representing patientmeasurements collected from the implantable pulse generator 101 (FIG. 1)during the initial period, as discussed in more detail below withreference to FIG. 5. The initially collected sensor data set 157 can beforwarded to the database module 151 for storage in the patient records,located at the memory 122. During subsequent, on-going monitoring of thepatient status, the pulse generator 101 periodically records asubsequently collected sensor data set 158, which is also forwarded tothe database module 151 for storage.

The database module 151 is configured to organize the individual patientrecords stored in the memory 122 and provide the facilities forefficiently storing and accessing the collected sensor data sets 157 and158 and patient data maintained in those records. Examples of suitabledatabase schemes for storing the collected sensor data sets 157 and 158in a patient record are described below with reference to FIG. 4. Any ofa variety of suitable database organizations can be utilized, includinga flat file system, hierarchical database, relational database, ordistributed database, such as those provided by database vendors,including Oracle Corporation of Redwood Shores, Calif.

The processing module 156 processes the initially collected sensor dataset 157 stored in the patient records to produce the patient preferences152. The patient preferences 152 include a set of preferencemeasurements 159 (e.g., body positions, the gross time of day, and/orother suitable sensor readings), which can be either directly measuredor indirectly derived from patient information. The patient preferences152 can be used to adjust the operating parameters for the pulsegenerator 101 and to monitor patient status on a continuous, ongoingbasis.

On a periodic basis (or as needed or requested), the processing module156 reassesses and updates the patient preferences 152. The databasemodule 151 can receive the subsequently collected sensor data set 158from the pulse generator 101 (FIG. 1) subsequent to the initial period.The processing module 156 re-assimilates the additional collected dataset into new patient preferences 152. The operations performed by theprocessing module 156 are described in more detail below with referenceto FIGS. 5 and 6.

The analysis module 153 analyzes the subsequently collected sensor dataset 158 stored in the patient records in the memory 122. The analysismodule 153 monitors patient status and makes an automated determinationin the form of a patient status indicator 154. Subsequently collectedsensor data sets 158 are periodically received from pulse generator 101and maintained by the database module 151 in the memory 122. Through theuse of this collected information, the analysis module 153 cancontinuously follow the patient status and can recognize any trends inthe collected information that might warrant medical intervention. Theanalytic operations performed by the analysis module 153 are describedin more detail below with reference to FIGS. 5 and 6. The feedbackmodule 155 can provide feedback to the patient based, at least in part,on the patient status indicator 154. For example, the feedback module155 may cause the pulse generator 101 to vibrate, to beep, and/or tooutput a warning message on the display 107 of the remote control 105(FIG. 1).

FIG. 4 is a database schema illustrating an organization of a patientpreference record 175 stored as a part of a patient record in the memory122 of the pulse generator 101 of FIG. 2. The patient preference record175 corresponds to the patient preferences 152 (FIG. 3). In theillustrated embodiment, only the information pertaining to the set ofpreference measurements in the patient preferences 152 are shown forpurposes of clarity. For example, as shown in FIG. 4, the patientpreference record 175 can include the following information: stimulationamplitude 176, frequency 177, electrode contact information 178, posture179, activity level 180, blood pressure 181, and time of day 182. Inother embodiments, the patient preference record 175 can also includepatient profile information, historical data, and/or other pertinentdata (not shown). During the initial (learning) phase, multiplepreferences 175 are collected for corresponding combinations of theforegoing parameters.

FIG. 5 is a flow diagram showing a method 200 for providing signals(e.g., blocking signals) to neuronal tissues in accordance with anembodiment of the present disclosure. In the illustrated embodiment, themethod 200 can include two phases: (1) collecting data and processingpatient preferences (e.g., in a learning phase, block 204), and (2)automatically applying stimulation based on the patient preferences,including updating the preferences as needed (block 210). The method 200can be implemented as a conventional computer program for execution bythe pulse generator 101 (FIG. 1). Even though the method 200 isdescribed below with reference to the therapy system 100 of FIG. 1, themethod 200 can also be practiced in other suitable systems forstimulating neuronal tissues.

As shown in FIG. 5, the method 200 can include programming the pulsegenerator 101 (FIG. 1) with an initial set of operating parameters(block 202). The initial set of operating parameters can include aplurality of programs corresponding to various patient statuses. Forexample, the initial set of operating parameters may include a firstprogram corresponding to the patient standing and a second programcorresponding to the patient lying down. The first and second programscan individually include an amplitude, a frequency, an electrode contactarrangement, and/or other suitable operating parameters for providingthe therapy signals to the patient. In certain embodiments, the programsare customizable. For example, the caregiver and/or the patient maycreate additional programs and/or modify existing programs to suit aparticular need.

The method 200 can also include establishing a preference or profile forthe patient during an initial period (block 204) e.g., during a learningphase. The preference can include preference values for the operatingparameters derived from recorded values for a particular patient status.For example, the preference may include a first preferred value for thestimulation amplitude when the patient is standing and a secondpreferred value when the patient is lying down. The preferences may alsoinclude baseline blood pressure, thoracic impedance, and/or otherphysiological indicators that give information about the patient status.Details of establishing the patient preferences are described in moredetail below with reference to FIG. 6.

The method 200 can further include using the data from the patientpreferences to automatically adjust the therapy applied to patient,e.g., during an automated operation phase. This phase can includemonitoring a patient status (block 206). In one embodiment, monitoring apatient status includes determining the current body position of thepatient with a gyroscope and indicating whether the patient is standingor lying down. In other embodiments, monitoring a patient status canalso include sensing the patient's current activity level, e.g., with anaccelerometer. In further embodiments, monitoring a patient status caninclude measuring the blood pressure, and/or other suitablephysiological parameters of the patient. In yet further embodiments,monitoring a patient status can include accepting a patient input using,for example, the remote control 105. Although such an input may not berequired of the patient in light of the automatic operation of thesystem, the system can receive patient inputs that may override orfacilitate the automatic operation.

The method 200 can also include determining whether a change in thepatient status has exceeded a preset threshold (block 208), e.g., thedelta threshold change, described previously. For example, thedetermination can be based on determining whether a subsequentmeasurement (e.g., lead impedance) exceeds a baseline value for aparticular patient status (e.g., standing) by a certain percentage(e.g., 20%) or a preselected value (e.g., 4000 ohms). In other examples,the determination can also be based on other suitable criteria. Thedetermination can be performed weekly, bi-weekly, at other periodicintervals, or on an as needed basis.

If the change in the patient status exceeds the preset threshold, themethod 200 includes determining whether reprogramming is necessary(block 209). In one embodiment, the pulse generator 101 can provide awarning signal to the patient indicating that the caregiver shouldperform a checkup. The caregiver can then determine whether the signaldelivery device 114 (FIG. 1) requires any physical adjustment. If so,then the caregiver may readjust the signal delivery device 114, and theprocess may revert to the initial programming stage at block 202. Ifnot, the process can revert to establishing the patient preferences atblock 204 and purging or overwriting at least a portion of the existingpatient preferences.

If the change in the patient status does not exceed the presetthreshold, the method 200 can adjust the stimulation based on themeasured patient status and the preferences in a closed-loop fashion(block 210). In one embodiment, adjusting the stimulation can includeselecting a setpoint for an operating parameter (e.g., the stimulationamplitude) of the pulse generator 101 based on the preference value fora particular patient status. For example, the setpoint for thestimulation amplitude can be set to the preferred value or can be offsetby a bias factor selected by the patient and/or the caregiver. In otherembodiments, adjusting the stimulation can also include accepting inputfrom the patient for increasing or decreasing the current stimulationlevel. In any of these embodiments, block 210 can include directing achange in the stimulation applied to the patient, based on thepreference established in block 204.

The method 200 can also include updating the preferences after theinitial period (block 212). For example, updating the preferences caninclude re-assimilating subsequent measurements for the patient statusand/or values of the therapy signals. The method 200 can further includedetermining whether the process should continue (block 214). If so, theprocess reverts to monitoring the patient status at block 206. If not,the process ends. The updating can be performed weekly, bi-weekly, inother periodic intervals, or continuously.

FIG. 6 is a flow diagram showing a method 204 for establishing patientpreferences in accordance with an embodiment of the present disclosure,e.g., during the learning phase described above. As shown in FIG. 6, themethod 204 can include at least one of monitoring the stimulation outputfrom the pulse generator 101 (block 216), monitoring a patient status(block 218), and recording a patient input (block 220). The method 204can also include correlating the monitored patient status to themonitored stimulation output (block 222). The stimulation output can becategorized based on readings from the sensing element 126. In oneexample, the stimulation output can be categorized based on whether agyroscopic reading from the sensing element 126 exceeds a predeterminedthreshold indicating the patient is standing, or below the predeterminedthreshold indicating the patient is lying down. The stimulation outputcorresponding to the patient as standing (or lying down) can then becalculated to derive the preference value for the particular patientstatus. In other examples, multiple thresholds and/or patient positionvalues corresponding to the thresholds may be used. In further examples,the stimulation output can be categorized based on other suitablepatient statuses. The method 204 can further include storing thecorrelated patient measurements as patient records (block 224) as shownin FIG. 4 in the memory 122 (FIG. 2) of the pulse generator 101.

The learning phase and/or the automatic operation phase can have othercharacteristics and/or other interrelationships in other embodiments.For example, in one such embodiment, the method 200 can includeprioritizing the patient's preferences during the learning phase andstoring this information for later use. In a particular example, themethod 200 can include ordering the patient preferences by the frequencywith which each preference is requested by the patient, and/or theduration that the preferred parameter value is in use. If the patientchooses “Program 4” most often when lying down, but then chooses“Program 2,” “Program 3” and “Program 1” in descending order, the methodcan include storing this information. Later (e.g., during the automaticoperation phase), if the patient manually overrides the now-defaultselection of “Program 4,” the method can include presenting the patientwith a preference-ordered list of next-best options, based on theinformation gathered during the learning phase. The options can bepresented in a variety of suitable manners, including a textual list ora graphical representation. Accordingly, if the patient becomesdissatisfied with the program selected as a result of the learningphase, the method can automatically provide likely backup programselections, without requiring the patient to reconsider every possibleprogram as an option. This can allow the patient to more quickly zero inon an effective new program if the existing program becomes lesssatisfactory, which may result e.g., if the implanted lead shifts ormigrates.

In another embodiment, the method 200 can implement the foregoingpreference tracking without necessarily making a clear distinctionbetween a learning phase and an operation phase. Instead, both phasescan be executed simultaneously. For example, the method 200 can includetracking patient preferences for a sliding period of time (e.g., oneweek or two weeks), and continuously updating the signal deliveryparameters and patient prioritization of programs. When the patientmanually overrides the automatically delivered program, the method canprovide a prioritized list of alternate programs, as discussed above.The list can be weighted by the frequency with which each program isselected and/or the duration each program is in use, as discussed above.In other embodiments, the list can be weighted in other manners. Forexample, the most recent patient selection can receive the highestpriority.

In still further embodiments, the foregoing meshed learning/operationphases can be implemented without tracking a prioritized list of patientpreferences. Instead, the method can include continuously updating theapplied signal delivery parameters based on feedback collected over aperiod of time (e.g., the past week, two weeks, or other period). If thepatient does not frequently provide manual input or feedback, the signaldelivery parameters can remain generally static. If the patientfrequently updates the parameters, the method can adjust the signaldelivery parameters accordingly, using an appropriate weighting scheme(e.g., greater weight given to the most recent patient request).

As described above, one or more impedance sensors can be used during thelearning phase to correlate patient status (e.g., patient posture and/oractivity level) with the patient's preferred stimulation parameters(e.g., therapy signal strength). The same impedance sensor or sensorscan subsequently be used to identify changes in patient state, inresponse to which the system can automatically adjust the operatingparameters with which the therapeutic signals are applied. FIGS. 7A-7Cgraphically illustrate representative embodiments in accordance withwhich impedance information may be used to control system operation.

Beginning with FIG. 7A, the patient may be implanted with a lead 702having multiple contacts 719 (illustrated as first-eighth contacts 719a-719 h) arranged along a lengthwise axis of the lead 702. Particularcontacts 719 or combinations of contacts 719 form part of a therapydelivery circuit, which also includes the patient's tissue, and viawhich the stimulation signals provide a therapeutic effect to thepatient. In addition to facilitating delivery of the therapeuticsignals, the circuit (e.g., the impedance of the circuit) can be used toidentify patient status and/or changes in the patient status. In aparticular example shown in FIG. 7A, circuit impedance is plotted as afunction of the contact identifier (a, b, c . . . h) for multiplepatient postures. When the patient assumes a first posture, theimpedance can be characterized by a first impedance profile 731, andwhen the patient assumes a second posture different than the firstposture, the impedance can be characterized by a second impedanceprofile 732. During the learning phase, the system can correlate patientpreferred stimulation parameters with patient posture, as identified bythe profiles 731 and 732. During the automatic operation phase, thesystem can identify a patient posture by matching, approximatelymatching, or otherwise linking measured impedance profiles with profilesobtained and stored during the learning phase. The system can thenautomatically apply patient-preferred signal strengths to each of thecontacts 719 a-719 h (or subsets of contacts) in a manner thatcorresponds to the preferred values established during the learningphase. The foregoing arrangement can be used for any number of postures,positions, and/or other patient states in accordance with a variety ofembodiments of the disclosure.

FIG. 7B illustrates an overall impedance profile 733 as a function ofcontact identifier, at a particular point in time for a particularpatient position. As shown in FIG. 7B, the overall impedance profile 733includes a capacitive component 734 a and a resistive component 734 b.Each of these components may have different values depending upon theparticular location along the lead 702 (FIG. 7A) at which the impedanceis detected or estimated. This information can be used, alone or inconjunction with other information, to identify patient status. Forexample, the resistance and/or capacitance associated with a particularcontact may be a function of the proximity of the contact to thepatient's soft tissue, bone structure, and/or cerebral spinal fluid. Ina particular example, the resistive component 734 b of the overallimpedance profile 733 may have a shape different than the capacitivecomponent 734 a, as shown in FIG. 7B, depending upon factors thatinclude the nature of the adjacent tissue. Accordingly, the system cancorrelate the capacitive and resistive profiles, and/or differencesbetween the capacitive and resistive profiles to identify patientstatus, such as patient posture. In one example, the impedance profileshown in FIG. 7B may correspond to the patient standing, as opposed tositting. The impedance profile can have other shapes, depending upon thelocation and orientation of the lead 702 within the patient's body. Inany of these embodiments, during the learning phase, the system cancorrelate patient preferences with capacitive and/or resistive profiles,and/or differences between the profiles, with different profilescorresponding to different patient statuses. After the learning phasehas been completed, the system can automatically implementpatient-preferred stimulation parameters based on the profilesdetermined from impedance inputs received from the lead 702.

In still further embodiments, the impedance (e.g., overall impedance,resistance, and/or capacitance) can also be tracked as a function oftime to identify patient status. For example, FIG. 7C illustratesimpedance as a function of time for a representative one of the contacts719 shown in FIG. 7A. Line 735 a indicates the impedance changing at amoderate rate, which may indicate that the patient is gradually movingfrom one position to another (e.g., bending). Line 735 b may becorrelated with a relatively slow or zero change in patient position,which can correspond to a different activity undertaken by the patient(e.g., sleeping). Line 735 c indicates that the patient is rapidlychanging posture in a cyclic manner, which can correspond to yet anotherpatient activity (e.g., walking, running or jumping). The rate of changeof the impedance function can be determined using suitabledifferentiation or other slope-determining techniques. The system canautomatically correlate patient preferences with the status informationidentified by the impedance characteristics shown in FIG. 7C during alearning phase, and can then automatically implement the patientpreferences during an automatic operation phase, based on impedancecharacteristics received from the lead 702.

In particular embodiments described above, the impedance characteristicsare identified via contacts that also provide the therapy signal. Theimpedance characteristics can be determined from a therapy signal, orfrom a separate signal applied to the therapy contacts. In otherembodiments, contacts that are not concurrently providing therapy,and/or other contacts (e.g., dedicated sensors), can be used to identifyappropriate impedance values. Representative techniques for detectingimpedance via implanted leads are disclosed in U.S. application Ser. No.12/499,769, filed on Jul. 8, 2009 and incorporated herein by reference.In other embodiments, impedance measurements can be used in mannersother than those described above. For example, the patient may havemultiple leads or other arrangements in which impedance sensors areremote from each other, and the impedance profile information can becollected from the multiple leads/sensors. Profiles may be stored in alookup table, profile bank or other suitable storage medium. The patientstatus can correspond to positions and/or activities other than thosedescribed above e.g., squatting, lying down on the patient's left side,lying down on the patient's right side, among others. In still furtherembodiments, the foregoing impedance profile information may be used incontexts other than spinal cord stimulation, e.g., peripheral nervestimulation therapy, or cardiac therapy.

Several embodiments of the systems and methods described above withreference to FIGS. 7A-7C were described in the context of profilesassociated with a single longitudinally-extending lead. In otherembodiments, the profiles can be established for axes other than alongitudinal axis, and/or for multiple axes. For example, the electrodearray 103 shown in FIG. 1, and/or an arrangement of multiple leadsplaced side-by-side, can be used to establish lateral profiles or atwo-dimensional map of impedance information.

Several embodiments of the methods discussed above can improve patientcomfort by allowing customization of the applied therapy signals. Forexample, the customization can include generating patient preferencesbased on previous measurements of the patient's preferences. Thepatient's comfort is further enhanced because several embodiments of themethods include detecting the patient's status and automaticallyadjusting a stimulation level of the applied therapy signals based onthe patient preferences without patient input. The foregoing arrangementcan reduce patient workload by automatically tracking the patient'sstimulation preferences and automatically adjusting the appliedstimulation parameters accordingly. In at least some embodiments, theprocess of adjusting the applied stimulation parameters based on patientpreferences is performed at the patient's implanted device. Thisarrangement can reduce or eliminate the need for the patient to interactwith any device other than the implant and the patient programmer.

From the foregoing, it will be appreciated that specific embodiments ofthe disclosure have been described herein for purposes of illustration,but that various modifications may be made without deviating from thedisclosure. For example, in certain embodiments, the pulse generator 101can include a plurality of integrated and remote sensing elements.Certain aspects of the disclosure described in the context of particularembodiments may be combined or eliminated in other embodiments. Forexample, in certain embodiments, the remote control 105 may be omitted,and the personal computer 110 may be operatively coupled to the antenna108 for communicating with the pulse generator 101. Further, whileadvantages associated with certain embodiments have been described inthe context of those embodiments, other embodiments may also exhibitsuch advantages, and not all embodiments need necessarily exhibit suchadvantages to fall within the scope of the disclosure. Accordingly, theinvention can include other embodiments not explicitly described orshown herein.

We claim:
 1. A method for treating a patient, comprising: collecting adata set at an implantable pulse generator, wherein the data setincludes: a plurality of impedance profiles, with individual impedanceprofiles including impedance data from multiple contacts of an implantedlead; and a plurality of values of a spinal cord stimulation parameter;identifying a particular value of the spinal cord stimulation parameterthat corresponds to one of the individual impedance profiles; and basedat least in part on receiving impedance data corresponding to theindividual impedance profile, automatically applying a therapy signalhaving the particular value of the spinal cord stimulation parameter toa spinal cord region of the patient, wherein collecting the data setincludes collecting a value of a capacitive component of an impedance,and collecting a value of a resistive component of the impedance.
 2. Amethod for treating a patient, comprising: collecting a data set at animplantable pulse generator, wherein the data set includes: a pluralityof impedance profiles, with individual impedance profiles includingimpedance data from multiple contacts of an implanted lead, and whereinthe plurality of impedance profiles include capacitive impedance values;and a plurality of values of a spinal cord stimulation parameter;identifying a particular value of the spinal cord stimulation parameterthat corresponds to one of the individual impedance profiles; based atleast in part on receiving impedance data corresponding to theindividual impedance profile, automatically applying a therapy signalhaving the particular value of the spinal cord stimulation parameter toa spinal cord region of the patient; and determining the status of apatient based at least in part on the capacitive impedance values. 3.The method of claim 2 wherein the individual impedance profilescorrespond to different postures of the patient.
 4. The method of claim2 wherein the plurality of values of a spinal cord stimulation parameterinclude values of a spinal cord stimulation parameter input by thepatient.
 5. A method for treating a patient, comprising: collecting adata set at an implantable pulse generator, wherein the data setincludes: a plurality of impedance profiles, with individual impedanceprofiles including impedance data from multiple contacts of an implantedlead wherein the plurality of impedance profiles include resistiveimpedance values; and a plurality of values of a spinal cord stimulationparameter; identifying a particular value of the spinal cord stimulationparameter that corresponds to one of the individual impedance profiles;and based at least in part on receiving impedance data corresponding tothe individual impedance profile, automatically applying a therapysignal having the particular value of the spinal cord stimulationparameter to a spinal cord region of the patient; and determining thestatus of a patient based at least in part on the resistive impedancevalues.
 6. A method for treating a patient, comprising: collecting adata set at an implantable pulse generator, wherein the data setincludes: a plurality of impedance profiles, with individual impedanceprofiles including impedance data from multiple contacts of an implantedlead; and a plurality of values of a spinal cord stimulation parameter;identifying a particular value of the spinal cord stimulation parameterthat corresponds to one of the individual impedance profiles;determining the status of the patient based at least in part on 1) theimpedance data, and 2) a signal from a sensing element; and based atleast in part on receiving impedance data corresponding to theindividual impedance profile, automatically applying a therapy signalhaving the particular value of the spinal cord stimulation parameter toa spinal cord region of the patient, wherein automatically applying atherapy signal is based on the determination of the status of thepatient.
 7. The method of claim 6 wherein the sensing element comprisesa gyroscope.
 8. A therapy system for treating a patient, comprising: asignal delivery device having a plurality of contacts; and animplantable pulse generator electrically coupleable to the signaldelivery device to apply a therapy signal to a spinal cord region of thepatient, wherein the implantable pulse generator includes a memory tostore therapy signal parameters and to store impedance data from aplurality of circuits, wherein individual circuits include at least oneof the contacts, wherein the impedance data include values of capacitiveimpedance and values of resistive impedance, and wherein the implantablepulse generator includes a computer-readable medium containinginstructions for performing a process comprising: analyzing the storedtherapy signal parameters and stored impedance data, wherein analyzingthe stored impedance data includes determining a rate of change ofimpedance for at least one individual circuit; and establishing aparticular value of a particular therapy signal parameter correspondingto particular stored impedance data.
 9. The therapy system of claim 8wherein the impedance data comprise an impedance profile having aplurality of impedance values, with individual impedance valuesassociated with corresponding individual circuits, and wherein theindividual impedance values include a value of a resistive component anda value of a capacitive component.
 10. A therapy system for treating apatient, comprising: a signal delivery device having a plurality ofcontacts; and an implantable pulse generator electrically coupleable tothe signal delivery device to apply a therapy signal to a spinal cordregion of the patient, wherein the implantable pulse generator includesa memory to store therapy signal parameters and to store impedance datafrom a plurality of circuits, wherein individual circuits include atleast one of the contacts, and wherein the implantable pulse generatorincludes a computer-readable medium containing instructions forperforming a process comprising: analyzing the stored therapy signalparameters and stored impedance data; and establishing a particularvalue of a particular therapy signal parameter corresponding toparticular stored impedance data, wherein the impedance data include animpedance profile having values of capacitive impedance, and wherein thevalues of capacitive impedance correspond to a posture of the patient.11. A therapy system for treating a patient, comprising: a signaldelivery device having a plurality of contacts; and an implantable pulsegenerator electrically coupleable to the signal delivery device to applya therapy signal to a spinal cord region of the patient, wherein theimplantable pulse generator includes a memory to store therapy signalparameters and to store impedance data from a plurality of circuits,wherein individual circuits include at least one of the contacts, andwherein the implantable pulse generator includes a computer-readablemedium containing instructions for performing a process comprising:analyzing the stored therapy signal parameters and stored impedancedata; and establishing a particular value of a particular therapy signalparameter corresponding to particular stored impedance data, wherein theimpedance data include an impedance profile having values of resistiveimpedance, and wherein the values of resistive impedance correspond to aposture of the patient.
 12. A therapy system for treating a patient,comprising: a signal delivery device having a plurality of contacts; andan implantable pulse generator electrically coupleable to the signaldelivery device to apply a therapy signal to a spinal cord region of thepatient, wherein the implantable pulse generator includes a memory tostore therapy signal parameters and to store impedance data from aplurality of circuits, wherein individual circuits include at least oneof the contacts, and wherein the implantable pulse generator includes acomputer-readable medium containing instructions for performing aprocess comprising: analyzing the stored therapy signal parameters andstored impedance data; establishing a particular value of a particulartherapy signal parameter corresponding to particular stored impedancedata, wherein the impedance data include a plurality of values ofcapacitive impedance; and receiving data corresponding to the pluralityof values of capacitive impedance and automatically applying a therapysignal having the particular value of the particular therapy signalparameter.
 13. A therapy system for treating a patient, comprising: asignal delivery device having a plurality of contacts; and animplantable pulse generator electrically coupleable to the signaldelivery device to apply a therapy signal to a spinal cord region of thepatient, wherein the implantable pulse generator includes a memory tostore therapy signal parameters and to store impedance data from aplurality of circuits, wherein individual circuits include at least oneof the contacts, and wherein the implantable pulse generator includes acomputer-readable medium containing instructions for performing aprocess comprising: analyzing the stored therapy signal parameters andstored impedance data; establishing a particular value of a particulartherapy signal parameter corresponding to particular stored impedancedata, wherein the impedance data include a plurality of values ofresistive impedance; and receiving data corresponding to the pluralityof values of resistive impedance and automatically applying a therapysignal having the particular value of the particular therapy signalparameter.
 14. An implantable pulse generator for treating a spinal cordregion of a patient, the implantable pulse generator comprising: adatabase module programmed to organize and store impedance data andstimulation parameters; and a processing module programmed to analyzethe stored impedance data and the stimulation parameters and establish abaseline containing a particular stimulation parameter corresponding toparticular impedance data, wherein the impedance data include values ofcapacitive impedance and values of resistive impedance.
 15. Theimplantable pulse generator of claim 14 wherein the processing module isfurther programmed to establish a patient status value based at leastpartially on the impedance data and corresponding to a patient activity.16. The implantable pulse generator of claim 14 wherein the processingmodule is further programmed to establish a patient status value basedat least partially on the impedance data and corresponding to a patientposture.
 17. The implantable pulse generator of claim 14 wherein theimpedance data include values of impedance as a function of time, andwherein the particular stimulation parameter corresponds to an activityof the patient.